Pneumatic drill.



A. IVI| BAIRD. PNEUMATIC DRILL. APPLlcATloN mit Nov.21. 191s.

Patented Apr. 1711917.

2 SHEETSSHEETl N mi Inventor A. M. BAIRD.

PNEUMATIC DRILL.

APPLCATION FILED NOV. 21.1916.

1,223,022. Patented .1111.111911 1 i 2 SHEETS-SHEET 2.

3i fl al? 3o L 30 L 10 /Jf/ f 10 Inventor ycordance with my invention,

UNITED STATES PATENT OFFICE.

A RUHIE M. BAIRD, OF TOPEKA, KANS. LS.

PNEUMATIC DRILL.

To all whom it may concern:

Beit known that I, Amrum M. BAIRD, a citizen of the United States, residing at To- 'eka, in the county of Shawnee and State of ansas, have invented certain new andvuseful Improvements in Pneumatic Drills, of which the following is a specification.

This invention is a portable drill having a pneumatic rotary motor of the reversible t e.

y1The object of the invention is to produce a drill of this character that is of extreme lightness considering its power, that has fewer parts than prior tools of similar general character, and whose wearing parts are of such extreme simplicity of design that they may beA easily repaired or replaced in any ordinary shop having use for the tool. The extreme simplicity is very important in that it enables shops to make their own repairs and replacements immediately without suffering from loss of use of the tool and without the necessity of carrying in stock many and expensive parts for repairs and replacements. A further object is to provide equally simple reversin means.

The invention consists o certain combinations relating to the piston blades, relating to the relation of the blades and rotary piston to the cylinder and .to the reversing valve, and relating to the compounding of the gearing; also to the means for taking up the end thrust of the working tool; also it comprises the parts, improvements and com binations hereinafter set forth and claimed.

In the drawings accompanying and forming part of this specification and in the description of the drawings, I have shown my invention in its preferred form and what I deem to be the best mode of applying the principles thereof; but it is to be understood that, within the scope of the appended claim, I contemplate changes in form, proportions, and materials, the transposition of parts, and the substitution Vof equivalent members, without departing from the spirlt of my invention.

Figure 1 is a central longitudinal sectional elevation of a pneumatic drill made in ac some of the parts being shown in elevation, the plane of the line 1 in Fig. 5. Fig. 2 is a cross section of the reversing valve plug on a plane indicated by the line 2 in Fig. 1. Fig. 3 is a sectional plan view of the rotary piston and Specification of Letters Patent.

Patented Apr. 17, 1917.

the blades taken `tpproximately on the plane indicated by the line 3 in Fig. 1. Fig. 4 is a sectional view (f the single piston blade on a plane indicatel by the line 4 in Fig. 3. Fig. 5 is a vertical cross sectional elevation Von a plane indi( ated approximately bythe line 5 in Fig. 1. Fig. 6 is a view of`the left-hand end (as seen in Fig. 1), the cover` plate being remived and the two spindles being shown in section on a plane indicated by the line 6 in Fig. 1, and the gears being shown partly by dotted outlines.

Similar refere ice characters indicate similar parts througiout the several views.

The c 7linder casing 7, which is formed with a cylinder bore 8 and closed at one end, is formed at its closed end with a gear housing 9. It is also formed with inlet and exhaust ports 10, 10, o ening into adjacent quarters of the cylin er, the cylinder bore bein tendlng over the respective quarters.

The rotary piston 12 is eccentrically mounted within the cylinder bore and bears against the side of the cylinder wall between the two ports s) as to seal them from each other. The pis ;on` is formed with two pairs of oppositely located lslots 13, 13, 13, 13, the

I slots of each pair being diametrically'oppo- Vbearing in the integral ead of the casing and which has a reduced extension 164 rojecting into tha gear housing and to w ich is keyed the pinion 17.

One pair of the piston blades is in con-` struction a sin le blade 18 of special form, its middle or web portion being of less length than its outer` or exposed portions by reason of the c it-away portions 20, 20. The other two bla les are separate but similar to each other, asshown at 19, 19, each being formed at each end with inward extensions 21, 21 which are of a size freely passing through the respective cut-away portions 20, 20 of the `angle blade. The slots form sufficient bearings for the single blade. To provide a sulii ciently long bearing for each end of the two -part blades, however, the ribs 22, 22 are fori ned in the piston to serve as formed with countersinks 11, 1l exguides and bearings for keeping the twopart blades in true radial alinement notwithstanding the air pressure and their -reciproeating movement radially of the piston. The cut-away portions 20, and the extensions 21, 21 are wholly witnin the interior of the piston in all positions of the pistons and blades. In the edge of each blade which contacts with the cylinder wall is formed a longitudinal groove 23 in which is fitted a radially movable packing strip 24. Two holes 25, 25 are drilled into the bottom of the groove from that side of the blade receiving the motive fluid when the tool is turnin to the right, and the packing strip is note ed above each hole, as shown at 26, to admit the air under it even when the strip is inextreme depressed position.

The valve casing 27 secured to the top of the cylinder'casing by means of screws,

28, is formed with a cylindrically bored opening` for receiving the valve plug 29, with ports 30, 30 leading from opposite sides of said opening to the respective ports 10, 10, with an exhaust port 32 through its base between the ports 30, 30, and with an intake port 31 opposite the exhaust port and communicating with the inlet pipe to be screwed into the threaded portion 43. The valve plug is formed with a flange 33 beai'in against one end of the valve casing aroun said opening and with a knob or handle 34 on the same end, a pin 35 projecting from said knob for convenient operation of the valve. The handle is located adjacent to the handle of the drill. The other end of the plug is formed with a reduced stem 36 whose terminal is further reduced and threaded for the reception of a nut 40. The stein 36 extends through a cap 38 which is counterbored for the reception of the compression spring 39 which bears between said cap and said nut for the purpose of compressing the flange 33 and the cap 38 against opposite ends of the valve casing, taking up the wear, and sealin the opening; the cap rotating with the p ug by reason of the engagement of the pin 41. The plug is formed with two passages 42, 42 .for directing the inlet and exhaust of the motive fluid. The openings of each passage are approximately ninety degrees from each other, center to center, and the adjacent openings of the two passages are similarly .spaced apart. In the central position of the plug, as shown in the drawings (see especially Fig. 5), both the inlet-port 31 and the exhaust 32 are closed. Turning the plug to the left forty-five degrees, the inlet port 31 is brought into cominunication with the right-hand port 30, and

the left-hand port 30 is openedl to the exhaust, thereby driving the motor 'to the right. By turning the plug ninety degrees, the communications are reversed so as to drive the motor to the left.

to the right' .cylinder wall.

'With the handle of th plug close to the supporting handle of the machine, it becomes very convenient for the operator to reverse the motor, as in withdrawin a tool.

An end plate or head 46 is fitte to the housing which contains the gears. A spindle'47, which bears in the integral cylinder head and in the cap 46 is formed integrally with a small gear 48, and keyed to the spindle is a larger gear 49 which mesheswitli the small pinion 17 on the piston spindle.

The gear 48 meshes with a large gear 50' which is integrally formed with a spindle 51 bearing in and projecting out of the boss 52 formed on the cap 46. The projecting portion 53 is reduced, and the spindle is terminally screw-threaded, as shown at 59. Loosely mounted on the reduced portion 53 is a washer or collar 55 which bears against the end of the boss, and adjacent to this collar are the two members of the ball bearing 56. A thrust collar 57` is screwed onto the screw-threaded terminal of the spindle, and held securely in place by set-screws 58 against the ball4 bearing member; whereby the end thrust of the working tool is borne by the casing through the boss, the collar, and the ball bearing, without being transmitted to the gearing or the rotary parts of the motor.

-Assumin the valve to be turned to the proper position for driving the motor to the right, it will be noted that the piston blade passing the lower edge of the countersink 11 will be impelled bythe motive fluid under full pressure during the next quarter turn, at the end of which the succeeding blade will close the inlet to the first-named blade and itself take the full pressure. During the next part of the turn, the first-named blade will present a greater area to the compressed air between the two blades than the area resented by the second-named blade, andp reason thereof will be propelled by the expanding air until it reaches the lower edge of the exhaust port 11', when the cylinder chamber back of the first-named blade becomes open to the exhaust. In similar manner, each blade in turn is propelled by the air under initial pressure and then by the -expanding air, thus compounding the mo- It will be noted, too, that the countor. tersink 11 for the exhaust extends circumferentially of the cylinder up substantially to the place of contact of the rotor with the This relieves the blade en tirely of back pressure during its last quarter or three-eighths turn'.

Upon reversing the motor2 the parts are driven in the opposite direction, and in the ,same manner, except that there is no compounding of the pressure; indeed, there is av slight compression; but this will not be materlal in view of the fact that the'motorwill usually be driven in the reverse only momentarily-as in withdrawing a tool bit. For a similar reason and in View of the' same fact, I provide the ports 25 only on the back sides of the blades when the blades are driven to the right. By the use of the packing strips, 1 avoid the necessity, and the use, of springs, depending not only on the centrifugal force for throwing the blades and vpackings against the wall of the cylinder,

but also on the air pressure under the packing strips immediately upon passing over the lower edge of the inlet port. The packing strips are thus forced to make perfect seals immediately upon passing the inletv Bort, notwithstanding the action of the lades under centrifugal force maybe somewhat sluggish.

Having thus what I claim is:

described my invention,

The combinatcn of a casing formed withV a cylinder bore and with inlet and exhaust ports, a hollow rotary piston eccentrically mounted in the cylinder bore and bearing against one side thereof, a single one-piece pair ofpiston bla des diametrically mounted in the piston, anc" a pair of separate piston blades radially mounted in said -piston at right angles to the oneiece blade,r said piston being formed with s ots for the reception of said blades andwith ribs for guiding the separate blades. n

In testimony whereof` I have axed my signature.

ARCHIE M. BAIRD. 

